1. Field of the Invention
The present invention relates generally to a method of producing a component of an automotive seat, and particularly to a method of producing a decorative outer cushion layer for a seatback. More specifically, the present invention is concerned with a method of producing an outer cushion layer which has a smoothly corrugated surface exposed to the outside.
2. Description of the Prior Art
Nowadays, some of the seats installed in passenger motor vehicles are of a type, which, as is shown in FIG. 5 of the accompanying drawings, provides a seatback "B" with a smoothly corrugated front surface "S" for not only giving a seat occupant a comfortable sitting posture but also improving an external appearance of the seat. The corrugated surface "S" is characterized by an outer cushion layer "CU" mounted on an inner cushion pad which is supported on a seatback frame. The outer cushion layer "CU" is provided by trimming a cushion material 20 which is shown in FIG. 8.
Hitherto, the cushion material 20 has been produced by the method as will be described in the following.
First, as is shown in FIG. 6, a plurality (viz., four in the illustrated case) of cushion pieces 10, 12, 14 and 16 of different sizes are prepared, each being of a flexible layered structure including a pad medium "b" made of a foamed material, an outer skin "a" bonded to an upper surface of the pad medium "b" and a base cloth "c" bonded to a lower surface of the pad "b". These cushion pieces are arranged in a given order by manual labor and, as is shown in FIG. 7, jointed to one another by stitching mutually facing edges of adjacent two thereof with a thread 18. With these steps, a cushion layer material 20 (viz., the cushion layer material with a corrugated outer surface) having three parallel channels "C" is produced. That is, parallel semicylindrical portions are formed on the cushion layer material 20. This cushion layer material 20 is then trimmed to a desired shape for its mounting to the inner cushion pad on the seatback frame.
However, the method as described hereinabove has the following inherent drawbacks.
Since the cushion pieces 10, 12, 14 and 16 are left separated before their jointing, placing them in the given order by manual labour is difficult or at least troublesome. Furthermore, selection of a proper piece from a cluster of the cushion pieces of different sizes is troublesome. This may sometimes induce misplacement of the cushion pieces, which would cause production of an inferior cushion material.